After the terminal metal bond pads are defined and etched on a semiconductor wafer, a passivation layer, generally SiO2, SiON, or SiN or combinations thereof, is deposited on the wafer to protect the die from chemical or mechanical damage, including that which may be incurred from the subsequent manufacturing process steps. In some processes, a stress buffer layer (SBL) is added, such as a polyimide, on top of the passivation layer.
Passivation-related processing is known to leave behind contaminant compounds including aluminum compounds on the bond pad surface. For example, in the case of a polyimide SBL, processing can cause various compounds to be formed on the bond pads, such as AlxFyOz. Such compounds on the bond pad surface are not desirable because they result in non-optimal wire bonds and cause the affected wafers to fail quality control wire-bondability testing or result in related failures over time. These defects are non-reworkable and the affected wafers or die are generally scrapped. Accordingly, effective methods for removing contaminants from aluminum-comprising bond pads are needed. Such methods should provide significantly enhanced bond pull strength and not result in significant undercut of the bond pads under the passivation layer.